Heretofore it has been the general practice to dry woods and other fibrous materials in a kiln or oven whereby the moisture in the material undergoing treatment is first converted into steam and thereafter said steam is removed. In those processes wherein the outer surfaces of said materials are dried first, any steam subsequently formed must pass through this dried outer zone with resultant cracking and splintering of the material. Additionally, in many woods, gums and resins are destroyed if the process is conducted at elevated temperatures thereby degrading the product or decreasing the market value thereof.